21 July 2019

The mystery of meadowhawks, redux

I'm a RuWhiChee! Read more here.

In 2010, we posted about the difficulties presented in identifying many Sympetrums, especially in eastern North America. With the increasing popularity of dragonfly ID and photography, and posting same on social media and citizen science websites, we have updated our post with some new data and references. I'll repeat the bottom line here, and you can read more at the original posting:

Over most of eastern North America, the most common meadowhawk species (Ruby, White-faced, Cherry-faced, and Jane's) should not or cannot be identified to species from a photograph -- especially when immature. Often, they cannot even be identified to species in the hand because the structural characteristics of their genitalia are intermediate due to hybridization. In fact, DNA analysis has shown that some of these "species" may not be full species, or may still be undergoing speciation.

08 July 2019

Alleghany River Cruiser persists

In 2014, Stylurus snagged one of several river cruisers at a site in southwest Michigan that proved to be Macromia alleghaniensis, Alleghany River Cruiser. Not only was this new for Michigan, but a little research indicated that it was the most northerly record for this species, as most other records north of 40 degrees were unconfirmed for various reasons, as described in the paper we published (available here).

Download a PDF of this paper here.

Despite multiple visits to the site in the intervening years, we (mostly he!) could not confirm that this species had a sustaining population at this site. Visits took place in mid-June to mid-July, and while he saw river cruisers there in 2016, he was could not net one to see what it was.

We stopped once again on 23 June this year, and were in luck when we saw river cruisers cruising this creek, the same place where the voucher was collected.

The two photos above show each side of the creek at a road crossing.
Water was much higher than in previous years.
The task of netting one was made a little easier when I stood on the road as the patrolling Macromia approached to cross the road to the other side. I could act as a spotter, and the dragonfly would usually turn back if it saw me standing there. In this way, Stylurus was able to net multiple river cruisers, all of which turned out to be M. alleghaniensis. Although we only saw one or two at a time, each time one was netted, another showed up (we held on to them until we were satisfied all were Alleghany before releasing all but two vouchers). We think there were at least 7 patrolling, and likely more. It was satisfying to know that this appears to be a healthy, sustaining population -- especially in a year with so much rain in spring and early summer that the creek was still running high.

I'm just posing here.

Identification and taxonomy of Macromias can be tricky (for a pretty thorough introduction, see Donnelly and Tennessen 1994). As with many ode identifications, structure trumps color pattern. One reliable character is the length of the mesotibial keel, a little "flange" on the middle leg, illustrated in this photo by Michael Moore. Much shorter on Alleghany than on similar M. illinoiensis.

Since our original discovery, a few other states have added this species to their lists after closer examinations of specimens. Two such revelations have been published in Argia: Brown and Thomas (2016) and Patten and Smith-Patten (2016). Links to all these resources are below.

Brown, G., and Thomas, M. 2016. Discovery of the Allegheny River Cruiser (Macromia alleghaniensis) in Rhode Island and Connecticut. Argia 28(2):9.

Donnelly, T. W., and K. J. Tennessen. 1994. Macromia illinoiensis and georgina: a study of their variation and apparent subspecific relationship (Odonata: Corduliidae). Bulletin of American Odonatology 2(3):27-61

Patten, M. A., and B. A. Smith-Patten. 2016. The Allegheny River Cruiser (Macromia alleghaniensis) in Oklahoma. Argia 28(3):12-14.